[core] Generate *.pyi stubs for protobufs

[tekumara]

Description

protoc can do this using --pyi-out see here

Use case

Example code that doesn't type check in vscode/pyright

def ping(address: str) -> ray_client_pb2.ClusterInfoResponse:
    with grpc.insecure_channel(address) as channel:
        stub = ray_client_pb2_grpc.RayletDriverStub(channel)
        return stub.ClusterInfo(ray_client_pb2.ClusterInfoRequest(type="PING"))

Errors with:

  /Users/tekumara/code/ray-demo/raydemo/ping.py:9:27 - error: Variable not allowed in type expression (reportInvalidTypeForm)
  /Users/tekumara/code/ray-demo/raydemo/ping.py:12:67 - error: No parameter named "type" (reportCallIssue)

ray 2.44.1

[tekumara]

See previous attempt #10042

[jjyao]

@tekumara do you want to take over that PR and make a contribution here?

[jclab-joseph]

+1